This invention relates to phase-control devices and methods and especially to electron-beam/semiconductor-diode means for independently controlling the phase of rf or microwave signals.
In the transmission of radar signals, antenna arrays are employed in which the phases of the signals radiated by the various antennas in the array are different so that a beam is formed in a certain direction. It would be desirable, also, to have a technique and means for varying the phases of the signals received by such an antenna array. A broadband antenna beam scanning technique does exist whereby, in theory, a compatible microwave receiver could be built. A strip transmission line whose conductors are separated by a ferroelectric dielectric is employed. The velocity of propagation along the transmission line is inversely proportional to the value of the dielectric constant of the insulator. A direct- current bias applied to this line, through the action of the ferroelectric coupling constants, changes the value of the dielectric constant and thereby varies the signal transit time. Unfortunately, the transmission velocity is varied. Another inherent limitation is the high loss tangent of the ferroelectric insulator which manifests itself in large signal attenuation.